1. Field of the Disclosure
The present disclosure relates to an organic light emitting display device, and more particularly, to an organic light emitting display device and a method of driving the same, which can reduce real-time sensing errors and thus increase an accuracy of real-time compensation.
2. Discussion of the Related Art
General organic light emitting display devices include a display panel, which includes a plurality of pixels respectively formed in a plurality of pixel areas defined by intersections between a plurality of data lines and a plurality of gate lines, and a panel driver that emits light from the plurality of pixels.
FIG. 1 is a circuit diagram for illustrating a pixel structure of a related art organic light emitting display device.
Referring to FIG. 1, each pixel of the display panel includes a first switching TFT ST1, a second switching TFT ST2, a driving TFT DT, a capacitor Cst, and an organic light emitting diode OLED.
The first switching TFT ST1 is turned on according to a scan signal (gate driving signal) supplied to a corresponding gate line GL. The first switching TFT ST1 is turned on, and thus, a data voltage Vdata supplied to a corresponding data line DL is supplied to the driving TFT DT.
The driving TFT DT is turned on with the data voltage Vdata supplied to the first switching TFT ST 1. A data current Ioled flowing to the organic light emitting diode OLED is controlled with a switching time of the driving TFT DT. A first driving voltage VDD is supplied to a power line PL, and, when the driving TFT DT is turned on, the data current Ioled is applied to the organic light emitting diode OLED.
The capacitor Cst is connected between a gate and source of the driving TFT DT. The capacitor Cst stores a voltage corresponding to the data voltage Vdata supplied to the gate of the driving TFT DT. The driving TFT DT is turned on with the voltage stored in the capacitor Cst.
A plurality of the sensing signal lines SL are formed in the same direction as that of the gate line GL. A second switch TFT ST2, which is turned on according to a sensing signal applied to a corresponding sensing signal line SL, is provided in plurality. The second switch TFT ST2 is turned on, and a current or voltage flowing in a corresponding organic light emitting diode OLED may be sensed by an analog-to-digital converter (ADC) of a data driver.
The organic light emitting diode OLED is electrically connected between the source of the driving TFT DT and a cathode voltage VSS. The organic light emitting diode OLED emits light with the data current Ioled supplied from the driving TFT DT.
The related art organic light emitting display device controls a level of the data current Ioled flowing from a first driving voltage VDD terminal to the organic light emitting diode OLED with a switching time of the driving TFT DT based on the data voltage Vdata. Therefore, the organic light emitting diode OLED of each pixel emits light, thereby realizing an image.
However, the threshold voltage (Vth) and mobility characteristics of the driving TFTs DT of the respective pixels are differently shown due to a non-uniformity of a TFT manufacturing process. For this reason, in general organic light emitting display devices, despite that the same data voltage Vdata is applied to the driving TFTs DT of the respective pixels, since a deviation of currents flowing in the respective organic light emitting diodes OLED occurs, it is unable to realize a uniform image quality.
To overcome such limitations, the display panel has been manufactured, and then, before a product is released, the display device performs an initial compensation operation that senses the characteristics of the driving TFTs of all the pixels, and compensates for a characteristic deviation of the driving TFTs of all the pixels.
FIG. 2 is a diagram for describing a display and sensing driving method of a related art organic light emitting display device. FIG. 2 illustrates a driving mode and sensing mode driving method after the display panel is released as a product.
Referring to FIG. 2, in the driving mode where an image is displayed, data voltages Vdata corresponding to image data are respectively supplied to the first data line to the last data line during a period of an Nth frame, thereby enabling an image to be displayed. Like this, when the display panel is driven to display an image, the driving TFTs are deteriorated.
The display device operates in the sensing mode, and compensates for a deterioration of the driving TFTs. The display device sequentially supplies a sensing signal in units of one horizontal line during a blank interval (about 350 us in the case of 120 Hz) between an nth frame and an n+1st frame to perform real-time sensing. The display device converts sensing data, generated by real-time sensing, into compensation data corresponding to a threshold voltage/mobility of the driving TFT DT of each pixel P. The display device compensates for the pixels in units of one horizontal line in real time using the compensation data.
In this way, the display device detects a threshold voltage/mobility of the driving TFT DT of each pixel of the display panel during the blank interval between a plurality of frames. The display device compensates for a characteristic of the driving TFT of each pixel using the compensation data based on the detected threshold voltage/mobility.
However, a real-time compensation scheme based on real-time sensing is short in sensing time, and thus is high in probability that an error occurs. Also, since sensing is affected by a data voltage, which is supplied to each pixel for displaying an image, an accuracy and reliability of sensing data is reduced. Also, since the display device is vulnerable to external factors such as a temperature (low temperature or high temperature), a change (surge voltage) in main power, dust, lightning, etc., a sensing error can occur, and for this reason, an accuracy and reliability of real-time compensation are low.